1. Field of the Invention
The present invention relates to a lead frame, and particularly to a lead frame to be used for a semiconductor integrated circuit and that is capable of preventing generation of any vacancy or void in a molded resin when the semiconductor circuit chip is encapsulated by the resin. p 2. Description of the Prior Art
FIGS. 5(A) and (B) show a prior art lead frame 1 to be used for a semiconductor integrated circuit. Lead frame 1 is provided with a base part 3 on which a semiconductor circuit device (chip) is to be mounted. Lead frame 1 comprises an inner lead part 5, an outer lead part 7 continued from inner lead part 5, and an outer frame part 9.
In this prior art lead frame 1, a semiconductor chip is mounted on the base part 3. Each bonding pad of the semiconductor chip and a corresponding inner lead node portion are connected by a bonding wire, and then resin molding is carried out within a metallic mold or the like which is not illustrated in FIG. 5 (A) or 5 (B). One-dot chain lines in FIG. 5 (A) indicate a cavity part 11 of the metallic mold and a gate part 13 for pouring a resin into the cavity part 11. FIG. 5 (B) shows a cross-sectional view taken from line 5B--5B of the gate part 13 and the cavity part 11. After the lead frame 1 having the semiconductor chip mounted thereon is set in the metallic mold, a resin is poured through the gate part 13.
However, in such a prior art lead frame, since a space between the gate part 13 and the inner lead is wide, a molding resin can flow relatively smoothly without obstacles, and the molding resin is apt to take in air when passing through the gate part 13. Besides, a pressure transfer efficiency to corners of the mold cavity part 11 near the gate part outlet is very low, therefore vacancies (voids) of the resin are very easily generated near the corners. Such voids could be improved to some extent by increasing the transfer rate and pressure of the molding resin and designing the shape of resin passageway in a transfer mold. However, these measures can not completely prevent the void. Besides, such measures also provide disadvantages. For example, that a wire flow of the inner lead will occur by the excessive increase of the transfer rate, and that a so-called mold flash may be produced due to the highness of the transfer pressure.